DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 129: Study of low-Z pellet shell ablation | ||
| Name: | Eric M. Hollmann ( |
Affiliation: | University of California, San Diego |
| Research Area: | Disruptions | Presentation time: | Requested | Co-Author(s): | T. Evans, A. James, P. Parks, J. Yu |
| Description: | An interesting possible approach to disruption mitigation is the delivery of large quantities of radiating impurities to the core plasma using low-Z shell pellets. Variations on this concept include shells filled with pressurized gas (proposed by T. Evans), filled with dust (proposed by P. Parks), or filled with a high-Z radiating material. The main concept is to deliver/disperse a large quantity of impurities on the magnetic axis with minimal edge radiation and current contraction. Successful implementation of these schemes requires an understanding of low-Z pellet shell ablation and the resulting edge current contraction. | ||
| Experimental Approach/Plan: | The lithium pellet injector with vertical launch can be used to inject different custom solid pellets into target discharges. Injected pellets can be designed with different thickness low-Z (e.g. C) shells and different core materials (e.g. LiF) with clear spectroscopic signatures. Monitoring of the pellet emission with different fast-framing camera filters would allow study of the pellet shell ablation rate by monitoring the brightness of the ablation plume and the pellet depth at which the shell material emission turned off. | ||
| Background: | Disruption mitigation experiments with small cryogenic pellets have been performed at DIII-D and elsewhere. Large runaway electron signals were seen when Ne and, especially, Ar, were used. However, the ability of solid shell pellets to delivery impurities into the plasma core without launching large MHD and without generating runaway electrons has not been studied. | ||
| Resource Requirements: | Lithium pellet injector, high-power H-mode discharges. | ||
| Diagnostic Requirements: | Fast-framing midplane camera with appropriate interference filters. | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | Custom shell pellets (to be made in cooperation with the GA inertial confinement group). | ||
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